EVALUATION OF PULMONARY SYSTEMIC BLOOD-FLOW USING ECG GATED ACQUISITION

We propose a functional parametric analysis method using ECG-gated Tc- 99m-labeled red blood cell (RBC) imaging for detection and characteriz ation of periodic variations in local blood activity in the lungs duri ng cardiac cycle. We validated in animal experiments that such count v ariations correlate with cyclical pulmonary blood flow and may be used for evaluation of systemic-to-pulmonary shunts. Clinical studies were performed in 48 patients, After labeling the RBC pool with Tc-99m, EC G-gated gamma camera images of both lung fields were acquired and proc essed to obtain Fourier transforms of time/activity functions in selec ted regions. The first harmonic parametric images of amplitude and pha se were derived. There was an excellent correlation (r = 0.92) between activity variations and pulsatile flow measured by our method with th at obtained by the thermodilution method in dog experiments (n = 10) a fter implantation of a systemic-to-pulmonary shunt. Patient studies sh owed the technique to be sensitive in detecting and quantifying abnorm al systemic-to-pulmonary blood flow. Lung pulsatile flow can thus be n oninvasively measured from functional parametric phase and amplitude i mages; the technique may be useful for detecting and quantifying abnor mal systemic-to-pulmonary blood flow in man.